Sweat Rings: Sweating the Details

An Indianapolis lab says it can help with summer running

I'm a sweater. By which I mean, you may think you sweat a lot, but that's only because you haven't run with me. If you had, you would understand what I mean when I say, "I'm a sweater." Over the years dozens of people have told me, "I bet I sweat as much as you." Then we've gone for a run, and they've conceded. What chance did they have against someone who once got squishy foot 18 minutes into a run? (If you must ask, "squishy foot" is when you sweat so much that your shoes make noise with every foot strike. And if you must ask, then you don't know what being a sweater is like.)

Being a sweater presents problems if you also like being a runner. Did I move to Maine from Maryland solely to escape near-daily meltdowns several months a year? Maybe not. But I will grant that it's easier to get through the long winters knowing that in summer I'll be able to finish most runs faster than at a stumble, and that for hours after my head won't be swimming and my productivity shot.

But I still have issues despite the move north, and can feel dead for weeks on end in the summer. So when I heard about a lab in Indianapolis that says it can improve performance via results from a sweat test, I booked a flight.

The St. Vincent Sports Performance facility performed its first sweat test in April of last year. A local athlete had repeated heat-related cramping, and couldn't find a commercially available product that prevented it. A small team, led by sport nutritionist Lindsay Langford and sports medicine physician Joel Kary, put together a way to emulate a procedure Gatorade makes available for its sponsored athletes: Collect an athlete's sweat, analyze its sodium and potassium concentration, and then make sport drink recommendations that best match the composition of the sweat. This customization, Langford says, helps to maintain electrolyte balance and decreases heat-related drops in performance.

From the follow-the-money department, this sort of sweat test started not with runners, but race horses. Initial tests on humans gathered sweat samples from the chest and forehead but, says Kary, it turns out sweat from those areas has higher sodium and potassium concentrations than the body's average. (This was learned by having cyclists ride trainers atop plastic tarps and then collecting the deposited sweat.) Over time, three sites for humans were settled on as reasonably representative: thigh, upper back and forearm. The average electrolyte concentration from those three areas, in turn, is said to represent your overall sweat composition.

Kary says that, while there's great variability from one person's composition to the next, for any individual it's not significantly affected by temperature or even how acclimatized to running in heat the person is. Langford adds that the saltiness of one's diet doesn't affect the sweat composition.

A sweat test at St. Vincent's costs $225, and starts with a nearly naked weigh-in.

Then Langford attaches small gauze pads to your thigh, forearm and upper back, covers them with tape, and sends you off to run on one of the facility's treadmills. I asked how long of a run was necessary, and she said long enough for the gauze pads to get saturated. I told her if that's all she needs, then with me we could wrap things up in 10 minutes, but I needed to get a run in anyway, so stayed on for 45 minutes.

After your run, it's back on the scale to see how much you sweated. I wasn't surprised to see I'd lost 2.4 pounds during my 6-miler, which translates to sweating 38.4 ounces in 45 minutes, or 51 ounces in an hour. This "sweat rate," as the science types call it, is environment-specific -- if it'd been hotter while I ran, I would have lost more, on a dry day you'll sweat less than on a humid day at the same temperature, etc. I've never really seen the point in these calculations given their run-to-run variability. And if your shoes squish when you run in the summer and your training partners complain that you're spraying them, you probably already know you're a heavy sweater.

The potentially useful part of the St. Vincent test, of course, is learning your sweat composition. After your run, Langford carefully removes the three patches, and squeezes each over a separate vial. ("Oh, that's good!" she said as she wrung the one from my arm into the tube.) The three vials are then sent to a lab in the United Kingdom for analysis; Langford says there's nowhere in the U.S. that will do the analysis for St. Vincent's, although a lab with the right equipment should open soon in Kentucky. (Yes, because of horse racing.)

Usually within two weeks, Langford gets the results back, sends you a sheet detailing your sweat composition and sets up a consultation. When she emailed mine, she wrote, "Your results were crazy high." By this she meant that an average athlete's sweat contains 70 millimoles of sodium per liter (mmol/L in the scientific shorthand). Mine contains 115.4 mmol/L. Convert that to milligrams, and you get 2,654.2 milligrams per liter. By way of comparison, Langford told me, the average American eats between 3,000 and 4,000 milligrams of sodium a day. During my moderately paced, not terribly warm 6-miler, I'd lost close to that amount.

Learning this was like the time I'd been running poorly for months and discovered I was anemic--here, coupled with my high sweat rate, was undeniable evidence that I wasn't just a head case or a wimp. "Your genetic value is that you're a really high-volume, salty sweater," Langford told me. "There's nothing you've done or didn't do that made you like that." So, everyone who's wondered why I'm so bad in the heat, you try finishing a 10-miler strong when you've lost more sodium than most people eat in a day!

Beyond comfort, the sweat test results provide guidance on how to proceed.

Langford sends recommendations on which commercial products most closely match your sweat. For me, short of running with a salt lick, she recommended SaltStick caps, each of which contains 215 milligrams of sodium. Langford advised putting three in a serving of sport drink or water before every summer run, and doing the same after, while drinking to thirst. She was also incredulous that in my 33 years of running I've almost never carried bottles in the summer. "We have to be realistic," she conceded. "With you, we're not going to get all that sodium in with a few drinks, but let's try to get close in a way that works for you."

Who knows, while you read this article in midsummer I might be pushing the pace at the end of a 90-minute run. My shoes will still squish, my shorts will still cling, but at the cellular level I might feel like a normal runner.

COOL CLOTHES!

Cooling apparel can improve performance in hot weather

After Deena Kastor won the bronze medal in the 2004 Olympic Marathon, the ASICS-sponsored runner did something remarkable: She gave partial credit to a Nike cooling vest. Kastor had worn the vest while sitting inside before the start of that scorching race in Athens, and later said that it helped her not only survive but thrive in the heat. There are now several brands of cooling apparel available. The theory for all is the same:

By lowering your core temperature before a hard workout or race, the apparel delays the onset of typical heat-related performance decreases. Studies on cyclists and runners have found various means of pre-cooling to increase distance covered in a set time or extend duration at a given intensity. The cooling elements of a piece of apparel, such as the gel packets inserted into compartments in Hyper Wear's cooling vest, can be stored in your freezer or, when traveling to a race, an ice chest.